Date: Thu, 13 Aug 2015 09:52:34 +0200 From: Agnieszka Bielec <bielecagnieszka8@...il.com> To: john-dev@...ts.openwall.com Subject: Re: PHC: Argon2 on GPU 2015-08-13 0:28 GMT+02:00 magnum <john.magnum@...hmail.com>: > On 2015-08-12 23:51, Solar Designer wrote: >> >> On Wed, Aug 12, 2015 at 11:45:35PM +0200, magnum wrote: >>> >>> On 2015-08-12 18:32, Agnieszka Bielec wrote: >>>> >>>> gws: 1024 3447 c/s 3447 rounds/s 297.022ms per >>>> crypt_all()+ >>>> Local worksize (LWS) 64, global worksize (GWS) 1024 >>>> using different password for benchmarking >>>> DONE >>>> Speed for cost 1 (t) of 1, cost 2 (m) of 1500, cost 3 (l) of 1 >>>> Many salts: 2925 c/s real, 307200 c/s virtual >>>> Only one salt: 2898 c/s real, 307200 c/s virtual >>> >>> >>> The benchmark figures (last two lines) are the correct ones. If you set >>> up auto-tune correctly, that speed should be similar to the benchmark. >>> For some formats/situations this is hard to achieve and it's just >>> cosmetic anyway. >> >> >> magnum, do you have an explanation why the best benchmark result during >> auto-tuning is usually substantially different from the final benchmark >> in most of Agnieszka's formats? I'm fine with eventually dismissing it >> as "hard to achieve" and "cosmetic anyway", but I'd like to understand >> the cause first. Thanks! > > > Generally a mismatch could be caused by using different [cost] test vectors > in auto-tune than the ones benchmarked, or auto-tune using just one repeated > plaintext in a format where length matters for speed (eg. RAR), or something > along those lines. > > Another reason would be incorrect setup of autotune for split kernels. For > example, if auto-tune thinks we're going to call a split kernel 500 times > but the real run does it 1000 times, we'll see inflated figures from > autotune. > > A third reason (seen in early WPA-PSK) is when crypt_all() does significant > post-processing on CPU where auto-tune doesn't. none of these I printfed plaintexts which are set during computation of gws and modified benchc.c to set the same values and result is the same
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